In recent years, in order to handle various large-volume data in various government, corporate and university institutions and other types of institutions, data has been managed using comparatively large-scale storage apparatuses. A large-scale storage apparatus of this kind is configured having a plurality of storage devices (hard disk drives and so on, for example) arranged in an array. For example, one RAID (Redundant Arrays of Independent Disks) group is configured from one or more hard disk drives, and one or more logical volumes are defined in a physical storage area provided by one RAID group. Furthermore, the logical volumes are provided to the host apparatus. The host apparatus is able to perform data writing and reading by transmitting predetermined commands to logical volumes.
In the foregoing storage apparatus, higher performance is required in order to process various large-volume data. Hence, in order to increase the performance of the storage apparatus, PTL1 discloses a technology according to which microprocessor packages (hereinafter called MPPK) which handle data processing to write and read data to/from logical volumes are determined beforehand and control information required for data processing is stored in the local memory in the MPPK. Here, an MPPK which handles the processing of a certain logical volume is called an owner MPPK and this MPPK is described hereinbelow as if it had ownership to the logical volume.
Furthermore, PTL1 discloses the fact that, if the data processing load varies from MPPK to MPPK, the MPPK processing load is distributed by changing the ownership of a certain logical volume to another MPPK. In addition, PTL2 discloses the fact that ownership is changed while I/O requests from the host apparatus are received. Accordingly ownership can be migrated without stopping task processing which is executed by the host apparatus.